Electric heating unit for clothes dryers

ABSTRACT

A heater box assembly for an electrically heated clothes dryer has a pair of spaced insulators with a wire heating element wound around the two insulators and with adjacent turns spaced apart. The support for the heating unit includes at least one spring acting on at least one insulator to apply a tension on the wire heating element to compensate for the change in length of the wire element due to thermal expansion. The box-like support is snugly received in a flanged opening of a wall of the dryer to form the heated air inlet for the dryer and mounting means including one or more tabs on the box for insertion into one or more corresponding slots in the flanged opening and a single fastener for securing the box at a side removed from the position of the slot or slots.

United States Patent Zenz [54] ELECTRIC HEATING UNIT FOR CLOTHES DRYERS[72] Inventor: Fred J. Zenz, Berrien Springs, Mich.

[73] Assignee: Whirlpool Corporation, Benton Harbor,

Mich.

[22] Filed: April 17, 1970 [21] Appl.No.: 29,388

Weingardt Kempston et al.

[15] 3,670,143 1451 June 13,1972

FOREIGN PATENTS OR APPLICATIONS 208,7l4 1/1956 Australia ..34/ l 33Primary ExaminerR. F. Staubly Attorney-James S. Nettleton, Thomas E.Turcotte, Burton H. Baker. Donald W. Thomas, Gene A. Heth, Franklin C.Harter, Anthony Niewyk, Robert L. Judd and Hill, Sherman, Meroni, Gross& Simpson [57] ABSTRACT A heater box assembly for an electrically heatedclothes dryer has a pair of spaced insulators with a wire heatingelement wound around the two insulators and with adjacent turns spacedapart. The support for the heating unit includes at least one springacting on at least one insulator to apply a tension on the wire heatingelement to compensate for the change in length of the wire element dueto thermal expansion. The boxlike' support is snugly received in aflanged opening of a wall of the dryer to form the heated air inlet forthe dryer and mounting means including one or more tabs on the box forinsertion into one or more corresponding slots in the flanged openingand a single fastener for securing the box at a side removed from theposition of the slot or slots.

12 Claims, 12 Drawing Figures FATENTEU R1 m2 7 (3)670, 143

sum 1 or s INVENTOR FQ JZ6ZZZ By f @Wgmmms PA'TENTEDM 13 1912 3. e70.143

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' sum 3 or 5 5 INVENTOR.

ffiedJZez Z BY 4 ATTORNEYS PKTENTED N 1 3 2 3.670 143 I 1 6112 2 22 2an" q b %vomtys BACKGROUND OF THE INVENTION being expensive tomanufacture and expensive to install it in an appliance such as a dryer.Many of the heating units used in dryers are disposed with the length ofthe wire of the heating unit running substantially parallel or at aslight angle to the direction of the air flow so that various sectionsof the heating element are in contact with air of different temperaturesand the unit develops hot spots which cause premature failure.

SUMMARY OF THE INVENTION The present invention provides a heater boxassembly of a box having means of mounting a heating unit therein.Preferably the heating unit comprises a wire element wound between apair of spaced insulators and mounting means, which biases the insulatorapart to compensate for thermal expansion, positioning the heating wirewith the wire element extending transverse to the air flow to preventunequal cooling of the wire element. In the preferred embodiment the boxis formed in sections which when secured together provide the mountingmeans for holding one of the insulators in a substantially rigidposition and the other insulator being free for relative movementthereto. The mounting means include springs disposed on the outside ofthe box for biasing the other insulator away from the one insulator. Thepresent invention also provides an expedient manner for attaching theheater box assembly to an appliance utilizing one or more coacting tabsand slots and a single retaining means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a rear view of a clothesdryer with portions broken away for, purposes of illustration showingthe heater box assembly of the present invention mounted therein;

FIG. 2 is a front view of a rear bulkhead of a dryer apparatus havingthe heater box assembly of the present invention mounted thereon;

FIG. 3 is an enlarged view of the heater box assembly of the presentinvention mounted on the back surface of a bulkhead with portions brokenaway for purposes of illustration;

FIG. 4 is a cross section taken along lines IVIV of FIG. 3;

FIG. 5, which is located on the sheet with FIG. 1, is an enlarged viewof a resilient mounting means used in the heater box assembly of FIGS. 3and 4;

FIG. 6 is an enlarged cross-sectional view of a tab and slot arrangementillustrated in the circle identified by VI in FIG. 4;

FIG. 7 is a view similar to FIG. 3 of an embodiment of the heater boxassembly of the present invention;

FIG. 8 is a crosssectional view taken along lines VIIIVIII of FIG. 7;

FIG. 9 is a view similar to FIG. 3 of a third embodiment of a heater boxassembly of the present invention;

FIG. 10 is a cross-sectional view taken along lines XI-XI of FIG. 10;

FIG. 11, which is located on the sheet with FIG. 1, is a crosssectionalview of an embodiment of an insulator of the present invention; and

FIG. 12 is a side view of the insulator of FIG. 11 with portions removedfor purposes of illustration.

assembly 2 DESCRIPTION OF THE PREFERRED EMBODIMENT Although theprinciples of the present invention can be utilized in a heater boxassembly for any apparatus, they are particularly useful in a heater boxassembly generally indicated at 15 attached to a laundry device such asan electrically heated dryer generally indicated at 16 in FIG. 1. Theelectrically heated dryer 16 has an outer casing 17 made up of a backpanel 18, a pair of side panels 19, 20 and a front panel notillustrated. Extending between the side panels Hand 20 and extendingparallel to the back panel 18 is a wall or bulkhead 21, which, as bestillustrated in FIG. 2, has an annular beaded embossment 22 formedthereon to receive a sealing means attached to the rear end of arotatable dryer drum (not shown). The bulkhead 21 is provided with anexhaust or outlet opening 23 which is covered by a grill and an ovalopening 24 having a peripheral flange 25 defining an inlet opening for aheating chamber defined by the front surface of the bulkhead and therotatable drum. The heater box assembly 15 is mounted on the bulkhead 21at the opening 24 to heat air entering the drying chamber. Disposed onthe rear side or surface of the bulkhead 21 is an air duct 26 (FIG. 1)in communication with the exhaust opening 23 and extending to a blowerhousing 27 which has an exhaust outlet 28. During the drying operation ablower mounted in the blower mounting 27 creates a suction causing airto enter the drying chamber by passing through the heater box 15 throughthe inlet opening 24 following the path of the arrows through theheating chamber to be withdrawn through the exhaust opening 23. Afterleaving the heating chamber through the exhaust opening 23, the air ispulled through the duct 26 to the blower housing 27 and expelled throughthe exhaust outlet 28 of the blower housing. An example of a laundrydryer and a description of its complete structure and operation is setforth in US. Pat. No. 3,398,465 which is assigned to the assignee ofthis application.

Referring to FIGS. 3 and 4, the heater box assembly 15 is made up of apair of metal members 30 and 31 each of which has deformed portions sothat when the two members are attached together they define a heatingchamber 32. Both the members 30 and 31 are preferably formed of sheetmetal by a metal stamping process which provides a peripheral edge orflange 33 and 34 respectively, which are used for securing the twomembers together in a conventional manner such as by fastening means 35.

The member 30, which has a dished or concave portion 36, has a series ofparallel louvers 37 extending across the bottom of portion 36, whichlouvers define inlet means for admitting air into the chamber 32. Themember 30 is also provided with an aperture 38 for receiving atemperature sensing means such as a thermostatic control of aconventional design.

The member 31 has a depressed portion of a cup shape with a bottom 40which has been further shaped to provide a projecting portion 41 with areversely bulged or indented bottom 42 which is provided with a patternof perforations 43 to define an air inlet for the drying chamber ofdryer 16. The projecting portion 41 has side walls 44 and has an ovalconfiguration complementary to the opening 24 in the bulkhead 21. Thesize of the projecting portion 41 is selected so that the side walls 44are received in the peripheral flange 25 in a snug engagement.

As best illustrated in FIG. 6, the side wall 44 is provided with a bend45 which abuts against an edge 46 of the peripheral flange 25 to limitinsertion of the portion 41 into opening 24. The side wall 44 is alsoprovided with a tab 47 which is inserted into slot 48 formed in theperipheral flange 25. The slot 48 and the tab 47 coact as shown in FIGS.4 and 6, to attach the lower end of the projecting portion 41 to theperipheral flange 25 of the bulkhead 21.

To complete the mounting or attachment of the heater box 15 in theopening 24, a retaining means generally indicated at 50 (FIG. 3)comprising a strap 51 which is attached at one end to the member 31 andat the other end carries a fastening means such as a screw 52 forsecuring the strap to the bulkhead 21. Thus, by engagement of thecoacting slot 47 and tab 48 and the single fastening means of theretainer 50, the box assembly is secured in the opening 24. It is to berealized that the coacting tab or tabs and slot or slots can be at otherlocations on the side wall 44 such as one side. The

retaining means 50 would be mounted opposite to the coact-- ing tab andslot retainer regardless of which portion of side wall 44 is utilized.

Disposed in the chamber 32 of the heater box assembly 15 is a heatingunit generally indicated at 53 including a pair of spaced elongated orbar insulators 54 and 55 and a wire heating element 56 which is wound orlooped around the pair of insulators 54 and 55 to provide wire loops orturns 57. Adjacent turns are spaced apart by axial spaced fins 58 oneach of the insulators 54 and 55. To anchor the wire heating element,the end turns 59 are passed by the upper insulator 54 on the oppositeside relative to the other turns 57 to form the cross wire configurationillustrated in FIG. 4. Each of the ends of the element 56 are thenpassed through the box assembly 15 by extending through a hollowinsulator 60 and is then connected to a source of electrical energy.Alternately, terminals may be welded or crimped to the ends of element56 with said terminals being retained by the hollow insulators 60.

To mount the insulators 54 and 55 of theheating unit 53 the members 30and 31 are provided with coacting mounting means which receive endportion 61 of the insulators 54 and 55, which end portions 61 have areduced diameter and a circumferential-groove 62. As illustrated, eachof the members 30 and 31 are provided with a pair of alignedsemi-circular cutout portions on the peripheral edge to form a pair ofcircular apertures or openings'63 to receive each of the end portions 61of the upper insulator 54 which end portions protrude from the heaterbox assembly 15. The openings 63 maintain the upper insulator 54 in asubstantially fixed position with respect to the heater box assembly 15.The lower insulator 55 has its reduced end portion 61 protruding fromthe heating chamber 32 and being received in elongated cutout portions65 and 66 formed respectively in the members 30 and 31 which cutoutportions 65 and 66 form an elongated aperture enabling relative movementof the insulator 55 when mounted.

The flanges 33 and 34 have portions removed at the respective cutoutportions to provide clearance for the end portions 61 of the insulators.It should be realized that insulators 54 and 55 could be provided withrectangular end portions rather than reduced diameter portions61. In theevent that rectangular end portions be provided, the members 30 and 31would be provided with appropriately dimensioned cutouts to receive themodified insulators.

To compensate for thermal expansion in the wire heating element 56,while in use, bearing means such as a pair of springs 69 are provided tomaintain a tensioning force on the loops 57 of the wire element 56 byurging the lower insulator 55 away from the upper insulator 54. As bestillustrated in FIGS. 3 and 5, each of the springs 69 has an end 70received by a notch on the exterior of the heater box assembly 15 andthe other end has a hook or loop 71 which is received in the groove 62of the end portion 61.

In operation, air drawn into the dryer chamber by the blower in theblower housing 27, is drawn through the louvers 37, which forms theinlet means of the heater box assembly 15, into the chamber 32. Astheair moves across. the loops 57 of the wire heating element, it isheated and then passes through the perforations 43 into the dryerchamber of the dryer 16. Since a tensioning force is applied to theloops 57 of the wire element 56 by the springs 69 pulling the lowerinsulator 55 away from the upper insulator,,any slack in the loop 57 ofthe wire element 56, which slack is the result of a change in length dueto thermal expansion, is removed by the tension applied by the springs69. By placing the springs on the exterior of the box assembly 15, thedeleterious effect of the heat emitted by the heating 1 element 56 onthe spring characteristics is minimized.

In FIGS. 8 and 9, an embodiment of the heater box assembly is generallyindicated at 15a which comprises a pair of members 300 and 31a attachedtogether to define a box means having a heating chamber 32a. Members 30aand 31a are substantially similar to the corresponding members 30 and 31 of the previously described'embodiment except they do not have cutoutportions on their. peripheral edges for providing support means formounting the insulators of a heating unit.

Disposed in the chamber 32a is a heating unit 53a which comprises anupper insulator 54a and a lower insulator 55a which are substantiallysimilar to the previously described insulators except their length issuch that the reduced end portions 61a are disposed in the chamber 32a.As in the previously described heating unit 53, a wire heating element56a is wound between the two spaced insulators 54a and 55a with turns orloops 57a which are spaced apart by fins 58a on each of the pair ofinsulators. The primary difference in the structure of the heater boxassembly 150 over the previously described embodimentis the mountingmeans for mounting the heating unit 53a in the chamber 32a. The mountingmeans comprises a pair of resilient members 74 which are attached byfastening means 75 to one of the members 30a or 31a and as illustratedto the member 30a. The resilient members 74 are provided with eye means76 at each end to engage a groove 62a formed in each of the reduced endportions 61a. The members 74 are of a spring character so that they biasboth the insulators 54a and 55a apart to maintain the desired tension onthe loops 57a of the wire heating element 56a.

As in the previously described embodiment, air enters through thelouvers 37a formed in the member 30a and flows substantiallyperpendicular to the plane formed by the wire loops 57 across the heaterelement 56a and then passes through the perforated bottom 42a oftheprojecting portion of the member 31a into the drying chamber formedby the bulkhead 21 and the tumbling drum of the laundry dryer 16.

A third embodiment of the heater box assembly is generally indicated at15b and illustrated in FIGS. l0 and 11. The heater box assembly 15b ismade up of a pair of members 30b and 31b which are interconnected at theperipheral edge in a manner similar to the previously describedembodiments to form a box structure having a heater chamber 32b. Themember 30b is provided with louvers 37b to admit air into the heatingchamber 32b and the member 31b is provided with a projecting portion 41bhaving a perforated indented bottom 42b which is complementary in shapeand size to be snugly received in a peripheral flange 25 of the opening24 of the bulkhead 21. As in the previously described embodiment ofFIGS. 8 and 9, a heating unit generally indicated at 53b comprising anupper cylindrical insulator 54b and a lower cylindrical insulator 55bwith the wire heating element 56b wound into turns or loops 57b thereonand between. As in the embodiment of FIGS. 8 and 9, the insulators 54band 55b are of a length so that they are completely contained within theheating chamber 32b.

To mount the heating unit 53b in the chamber 32b, two pairs of brackets80,80, 81,81, respectively, are attached to one of the members and asillustrated attached to the member 30b. Each of the brackets 80 has aslot 82 opening in the upward direction towards a top of the heater boxassembly 15b. The lower pair of brackets 81 have a slot 83 opening in adirection opposite to the slot 82 and opening at a direction towards thebottom of the heater box 15b. As illustrated, the upper insulating 54bis supported in the pair of brackets 80 with its reduced end portions61b received in the slots 82. The lower insulator 55b has reduced endportions 61b which are received in the slots 83. The reduced endportions 61b of both insulators 54b and 55b are provided with grooves62b which prevent axial shifting of the insulators in the brackets.

' To bias the pair of insulators 54b and 55b away from each other, aresilient spring 86 is anchored to an eye 87 attached to the interior ofthe chamber 32b and as is illustrated is attached to a lowerwall 88 ofthe member 30b. The other end 89 of the resilient spring 86 is attachedto a wire loop 90 which is received in a groove 91 formed at the centerof the insulator 55b. The spring means 86 applies a tension to the loops57b to maintain the upper insulator 54b in abutting relation with thebottom of the slots 82 and to maintain a desired tension on the wireelement 56b to compensate for the expansion during heating of theheating unit.

In each embodiment, the heating unit 53, 53a or 53b can be formed bywinding the wire element around the two spaced insulators. Then the unitis installed in the box structure with a minimum amount of labor. It iscontemplated that a disposable spacer can be utilized to hold the twoinsulators such as 54 and 55 the desired distance apart to prevent anyentanglement of the wire loops of the heating element. In theembodiments of FIGS. and 11 one pair of brackets which can be thebrackets 80 or the brackets 81 will need to be assembled onto the member30b after the other pair has received its respective insulator.

In each of the embodiments the air enters the louvers on the member 30,30a or 30b and passes in a direction substantially perpendicular to thedirection of the wires 56 and out through the perforated bottom 42 intothe drying chamber. By having the air flow in this manner, each of thewire elements is contacted by air of substantially the same temperatureso that the desired cooling is obtained throughout the heating elementto eliminate the occurrence of any hot spots thereon. Such coolingenables the use of wires of alloys such as iron base alloys to operateat a lower heating temperature and therefore enables the construction ofthe heating unit 53 using a material which is more economical andavailable than used in prior heating elements which are typically nickelbased wire alloys. Since the two insulators 54 and 55 are mounted with ameans biasing them apart to maintain the desired tension on the wireelement 56, the element can be a straight wire instead of the helicallyturned wire of the previous heating units and the tensioning preventssagging or buckling of the wire during a heating operation andeliminates the possibility of shorting between turns or loops due tobuckling or sagging of the wire.

An alternate embodiment of the insulator generally indicated at 93 isillustrated in FIGS. 12 and 13. The insulator 93 is provided with fins94 which are axially spacedalong its length to maintain wire loops 95 inspaced relationship to prevent their accidentally contacting orshorting. In between each of the fins 94 the insulator 93 has apassageway 96 toenable a flow of air to cool the insulator. Asillustrated in FIG. 13, a portion of each wire loop 95 overlies thepassageway 96 to receive the effect of the cooling air. In the design ofthe insulator 93, only a small portion 98 of each wire loop 95 is incontact with the solid portion of the insulator 93. Thus, the

wire loops 95 receive additional cooling to prevent the creation of hotspots thereon during a heating operation.

Each of the embodiments such as the units 15, a and 15b are providedwith a tab for acting with a coacting slot on the flange of the openingin the bulkhead 21 and the retainer means 50. Thus the unit or heaterbox assembly 15, 15a or 15b can be easily assembled onto the bulkhead 21of the dryer device 16. The present structure of the unit not onlysimplifies the manufacturing of the heating elements 53 and its assemblyinto the box formed by the members and 31, but also simplifies theinstallation of the heating box assembly 15 onto' the bulkhead 21whether during initial installation or in a subsequent removal andinstallation of repair parts.

Although minor modifications might be suggested by those skilled in theart, it should be understood that I wish to embody within the scope ofthe patent warranted hereon all such modifications as reasonably andproperly come within the scope of my contribution to the art.

I claim as my invention:

l. A heater box assembly for a laundry appliance such as an electricallyheated clothes dryer, comprising:

a first member having means for forming an air inlet for the laundryappliance; I

a second member attached to said first member to provide a box meanshaving an enclosed heating chamber, said second member having means forforming an air inlet to the chamber;

a heating means including a pair of insulators and a wire heatingelement wound about the insulators with adjacent turns being spaced fromeach other; and

means for mounting said heating means in the heating chamber with a pairof insulators in spaced relationship and with the ends of each insulatorprotruding therefrom including biasing means for urging the pair ofinsulators away from each other thereby applying a tension on the wireto compensate for the thermal expansion of the wire;

said mounting means including aligned cutout portions in each of saidfirst and second members coacting together as the members are assembledto provide an aligned pair of apertures to receive the protruding endsof each of said pair of insulators with one of the pair of aperturesmaintaining one of the pair of insulators substantially rigid in saidchamber and the other pair of apertures being shaped to enable relativemovement of said other insulators away from the one insulator under theurging of said biasing means to maintain the wire heating element undertension.

2. A heater box assembly in accordance with claim 1, wherein the wireheating element is of a material of an iron base.

3. A heater box assembly according to claim 1, wherein said biasingmeans comprises a pair of springs disposed on the outside of the heatingchamber, each of said springs being anchored to the box means formed bysaid first and second members and attached to a protruding end of saidother insulator so that said springs are removed from the heat generatedby the wire heating element to prevent the deleterious effect of theheat thereon.

4. A heater box assembly according to claim 1, wherein said bias meanscomprises a resilient spring anchored to said box means and attached tothe other of said pair of insulators.

5. A heater box assembly for a laundry appliance such as an electricallyheated clothes dryer comprising:

a first member having means for forming an air inlet for the laundryappliance; v

a second member attached to said first member to provide a box meanshaving an enclosed heating chamber. said second member having means forforming an air inlet to the chamber;

a heating means including a pair of insulators and a wire heatingelement wound about the insulators with adjacent turns being spaced fromeach other; and

means for mounting said heating means in the heating chamber with a pairof insulators in spaced relationship including biasing means comprisinga resilient spring anchored to said box means and attached to one ofsaid pair of insulators for urging the pair of insulators away from eachother thereby applying a tension on the wire to compensate for thethermal expansion of the wire, said means for-mounting said pair ofinsulators comprising brackets attached to one of said first and secondmembers, each of said brackets having a slot for receiving an end ofsaid insulators, said brackets being arranged in pairs with the slots ofone pair opening in a direction opposite to the slots of the other pairso that the resilient spring holds the other of said pair of insulatorsagainst the base of the slots of the one pair of brackets while the oneinsulator is urged away from the base of its slots of the other pair ofbrackets.

6 A heater box assembly according to claim 1, wherein each of theinsulators of said pair are cylindrical members provided with axiallyspaced fins to maintain separation between adjacent turns of the wireheating element thereon.

7. A heater box assembly according to claim 6, wherein each of saidinsulators has passageways extending between each of the axially spacedfins to enable the passage of air therethrough for cooling of saidinsulator.

8. A heater box assembly according to claim 1, wherein the means formingthe inlet-in the first member has a shape complementary to an opening ina wall of the laundry device and is adapted to snugly fit therein; andfurther including means for mounting the heater assembly in said openingcomprising a tab disposed on said first member coacting with a slotadjacent the opening in the wall, and a fastening means disposed on saidbox a substantial distance from the coacting tab and slot whereby theheater box assembly is mounted in the opening by engaging the tab in theslot and then securing the fastening member to the wall of the laundrydevice.

9. A heater box assembly for a laundry appliance such an electricalheated clothes dryer, comprising:

a first member having means for forming an air inlet for the laundryappliance;

a second member attached to the said first member to provide abox meanshaving an enclosed heating chamber,

,said second member having means for forming an inlet to the chamber;

a heating means including a pair of insulators and a wire heatingelement wound about the insulator with adjacent turns being spaced fromeach other; and

means for mounting said heating means in the heating chamber with thepair of insulators in spaced relationship, said means for mountingincluding biasing means for urging both of the insulators of said pairin a direction away from each other thereby applying a tension on thewire to compensate for the thermal expansion of the wire.

10. A heater box assembly in accordance with claim 9, wherein saidmounting means comprises resilient spring means attached to one of saidfirst and second members and resiliently mounting each of said pair ofinsulators in the heating chamber.

11. A heater box assembly according to claim 1, wherein said mountingmeans disposes said heating means in the heating chamber with the flowof air substantially perpendicular to the direction of the wire heatingelement thereby eliminating hot spots on the heating element.

12. A heater box assembly for a laundry appliance such as anelectrically heated clothes dryer, comprising:

a first member having means for forming an air inlet for the laundryappliance;

a second member attached to said first member to provide a box meanshaving a heating chamber, said second member having means for forming anair inlet to the chamber;

a heating means including a pair of insulators and a wire heatingelement of an iron base material wound about the insulators withadjacent turns being spaced from each other;

each of said pair of insulators being a cylindrical member havingaxially spaced fins to maintain separation between adjacent turns of thewire heating element and each'insulater having passageways extendingbetween each of the spaced fins to enable passage of air therethroughfor cooling the insulator; and

means for mounting said heating means in the heating chamber with the.pair of insulators in spaced relationship including biasing means forurging the pair of insulators away from each other thereby applying atension on the wire to compensate for the thermal expansion of the wire;said mounting means comprising means defining cutout portions in both ofsaid first and second members, said cutout portions being arranged inaligned pairs so that the attachment of said first and second memberforms pairs of aligned apertures to assemble said pair of insulators inthe desired position in the heating chamber, one pair of said pairs ofapertures receiving the endsof one of said pair of insulators andmaintaining said one insulator in a substantially fixed positionrelative to said heating chamber, the other of said pair of apertureseach having an elongated configuration to receive the ends of the otherinsulator of said pair of insulators and enabling relative movement ofthe other insulator away from the one insulator and relative to saidheating chamber; and

said biasingmeans comprising a pair of springs disposed on the outsideof the heating chamber, each of said springs being anchored to the boxmeans formed by said first and second members and attached to aprotruding end of said other insulator so that said springs are removedfrom the heat generated by the wire heating element to prevent thedeleterious effect of the heat thereon.

1. A heater box assembly for a laundry appliance such as an electricallyheated clothes dryer, comprising: a first member having means forforming an air inlet for the laundry appliance; a second member attachedto said first member to provide a box means having an enclosed heatingchamber, said second member having means for forming an air inlet to thechamber; a heating means including a pair of insulators and a wireheating element wound about the insulators with adjacent turns beingspaced from each other; and means for mounting said heating means in theheating chamber with a pair of insulators in spaced relationship andwith the ends of each insulator protruding therefrom including biasingmeans for urging the pair of insulators away from each other therebyapplying a tension on the wire to compensate for the thermal expansionof the wire; said mounting means including aligned cutout portions ineach of said first and second members coacting together as the membersare assembled to provide an aligned pair of apertures to receive theprotruding ends of each of said pair of insulators with one of the pairof apertures maintaining one of the pair of insulators substantiallyrigid in said chamber and the other pair of apertures being shaped toenable relative movement of said other insulators away from the oneinsulator under the urging of said biasing means to maintain the wireheating element under tension.
 2. A heater box assembly in accordancewith clAim 1, wherein the wire heating element is of a material of aniron base.
 3. A heater box assembly according to claim 1, wherein saidbiasing means comprises a pair of springs disposed on the outside of theheating chamber, each of said springs being anchored to the box meansformed by said first and second members and attached to a protruding endof said other insulator so that said springs are removed from the heatgenerated by the wire heating element to prevent the deleterious effectof the heat thereon.
 4. A heater box assembly according to claim 1,wherein said bias means comprises a resilient spring anchored to saidbox means and attached to the other of said pair of insulators.
 5. Aheater box assembly for a laundry appliance such as an electricallyheated clothes dryer comprising: a first member having means for formingan air inlet for the laundry appliance; a second member attached to saidfirst member to provide a box means having an enclosed heating chamber,said second member having means for forming an air inlet to the chamber;a heating means including a pair of insulators and a wire heatingelement wound about the insulators with adjacent turns being spaced fromeach other; and means for mounting said heating means in the heatingchamber with a pair of insulators in spaced relationship includingbiasing means comprising a resilient spring anchored to said box meansand attached to one of said pair of insulators for urging the pair ofinsulators away from each other thereby applying a tension on the wireto compensate for the thermal expansion of the wire, said means formounting said pair of insulators comprising brackets attached to one ofsaid first and second members, each of said brackets having a slot forreceiving an end of said insulators, said brackets being arranged inpairs with the slots of one pair opening in a direction opposite to theslots of the other pair so that the resilient spring holds the other ofsaid pair of insulators against the base of the slots of the one pair ofbrackets while the one insulator is urged away from the base of itsslots of the other pair of brackets.
 6. A heater box assembly accordingto claim 1, wherein each of the insulators of said pair are cylindricalmembers provided with axially spaced fins to maintain separation betweenadjacent turns of the wire heating element thereon.
 7. A heater boxassembly according to claim 6, wherein each of said insulators haspassageways extending between each of the axially spaced fins to enablethe passage of air therethrough for cooling of said insulator.
 8. Aheater box assembly according to claim 1, wherein the means forming theinlet in the first member has a shape complementary to an opening in awall of the laundry device and is adapted to snugly fit therein; andfurther including means for mounting the heater assembly in said openingcomprising a tab disposed on said first member coacting with a slotadjacent the opening in the wall, and a fastening means disposed on saidbox a substantial distance from the coacting tab and slot whereby theheater box assembly is mounted in the opening by engaging the tab in theslot and then securing the fastening member to the wall of the laundrydevice.
 9. A heater box assembly for a laundry appliance such anelectrical heated clothes dryer, comprising: a first member having meansfor forming an air inlet for the laundry appliance; a second memberattached to the said first member to provide a box means having anenclosed heating chamber, said second member having means for forming aninlet to the chamber; a heating means including a pair of insulators anda wire heating element wound about the insulator with adjacent turnsbeing spaced from each other; and means for mounting said heating meansin the heating chamber with the pair of insulators in spacedrelationship, said means for mounting including biasing means for urgingboth of the insulators of said paiR in a direction away from each otherthereby applying a tension on the wire to compensate for the thermalexpansion of the wire.
 10. A heater box assembly in accordance withclaim 9, wherein said mounting means comprises resilient spring meansattached to one of said first and second members and resilientlymounting each of said pair of insulators in the heating chamber.
 11. Aheater box assembly according to claim 1, wherein said mounting meansdisposes said heating means in the heating chamber with the flow of airsubstantially perpendicular to the direction of the wire heating elementthereby eliminating hot spots on the heating element.
 12. A heater boxassembly for a laundry appliance such as an electrically heated clothesdryer, comprising: a first member having means for forming an air inletfor the laundry appliance; a second member attached to said first memberto provide a box means having a heating chamber, said second memberhaving means for forming an air inlet to the chamber; a heating meansincluding a pair of insulators and a wire heating element of an ironbase material wound about the insulators with adjacent turns beingspaced from each other; each of said pair of insulators being acylindrical member having axially spaced fins to maintain separationbetween adjacent turns of the wire heating element and each insulatorhaving passageways extending between each of the spaced fins to enablepassage of air therethrough for cooling the insulator; and means formounting said heating means in the heating chamber with the pair ofinsulators in spaced relationship including biasing means for urging thepair of insulators away from each other thereby applying a tension onthe wire to compensate for the thermal expansion of the wire; saidmounting means comprising means defining cutout portions in both of saidfirst and second members, said cutout portions being arranged in alignedpairs so that the attachment of said first and second member forms pairsof aligned apertures to assemble said pair of insulators in the desiredposition in the heating chamber, one pair of said pairs of aperturesreceiving the ends of one of said pair of insulators and maintainingsaid one insulator in a substantially fixed position relative to saidheating chamber, the other of said pair of apertures each having anelongated configuration to receive the ends of the other insulator ofsaid pair of insulators and enabling relative movement of the otherinsulator away from the one insulator and relative to said heatingchamber; and said biasing means comprising a pair of springs disposed onthe outside of the heating chamber, each of said springs being anchoredto the box means formed by said first and second members and attached toa protruding end of said other insulator so that said springs areremoved from the heat generated by the wire heating element to preventthe deleterious effect of the heat thereon.